Third Generation Partnership Project (3GPP) release 8, Evolved Universal Terrestrial Radio Access (EUTRA), also called long-term-evolution (LTE), supports different downlink multi-antenna modes. These modes include: (1) transmit diversity, (2) code book-based pre-coding for both single-user and multi-user spatial multiplexing, and (3) user equipment (UE) (a.k.a., a mobile terminal) specific reference signal assisted, single-rank, non-code book-based beam-forming.
In code book based pre-coding, the pre-coding code books at an eNodeB (eNB) are predetermined. In a non-code book based beam-forming mode, downlink transmitting weights may be determined in the eNB based on UE uplink signals (e.g., reference signals) or in the UE together with feedback of the downlink transmission weights from the UE to the eNB. An instantaneous eNB transmission weight is decided for each scheduled UE, either based on UE pre-coding matrix indicator (PMI) feedback or on a UE reference signal.
Wireless networks are increasingly employing multi-antenna solutions and/or signal forwarding nodes (e.g., repeaters, relays, etc.) to increase coverage area and/or user data rates. However, because an eNB's code book is predetermined and the non-code book method of determining beam-forming weights is UE-specific and dynamically varying, it is difficult to ensure an effective combination of signal forwarding nodes and multi-antenna schemes.
Accordingly, improved systems and methods are desired.